I have this DAC for many years. It use TDA1541 for D/A Convension. I had modified on OP and output capacitance. The sound was very good after modification. Well, it's broken few years ago. The major problem on left chennal appeared high frequncy noise when I listening music. The sound from left chennal became fuzz. So, I decided to use D-500 as a switch for different digital signal input. Anyway, I would like to asked for help to solve. Any suggestion are welcome.